Audyssey is not a silver bullet that will solve all problems, but at least in my case Audyssey XT32 certainly improves the sound in general as the possible placement of speakers (LCR, surround) and subwoofers is very limited along with a difficult room.
Audyssey is quite picky with respect to measurements locations, and "where did the bass go" has happened to me more than once.
Is it a placebo effect as one poster suggest? When I toggle XT32 on/off from my remote control the effect is obvious, but not for all types of content and it is not an improvement for all content either.
My preference is to have an excellent room with total freedom where to place speakers/subwooofers/room treatment, but alas, life is hard and then you die.